Biology Reference
In-Depth Information
Figure 14.11.
Schematic representation of the DNA-pectin templated
silver nanowire formation between two interdigitated electrodes.
a silicon substrate with 500 nm gaps between the electrodes. The
siliconsubstratebetweentheinterdigitatedelectrodeswasmodified
with3-aminopropyltriethoxysilane,asshowninFig.14.11,allowing
cross-linking to amine terminated PNA probes. Upon binding of
target DNA, zirconium-phosphate-carboxylate chemistry was used
to bind the polysaccharide and pectin to the DNA. Oxidation of
the pectin under acidic conditions yielded aldehyde groups which
served as sites for silver deposition via Tollen's reduction. The
formation of the DNA templated silver nanowires significantly
reduced the resistance measured between the interdigitated elec-
trodes allowing detection of DNA as low as 3 fM. Use of DNA as
a template for growth of silver nanoclusters was also reported by
Wang's lab [55]. In this work, ssDNA probes were immobilized
via carbodiimide chemistry to cystamine modified Au electrodes.
Following binding of target DNA, silver ions were loaded onto the
DNA by Na
+
/Ag
+
exchange/electrostatic interactions under basic
conditions.Hydroquinonewasthenusedtocatalyzesilverreduction
forming DNA templated silver nanoclusters. These aggregates were
